Both large and small animals have to be handled for animal husbandry and veterinary purposes, and these animals include not only domestic and farm and station animals, but also feral and wild animals. Thus in these situations it is necessary to hold or restrain the animal, and conventionally this has been accomplished by manually handling the animal or by using mechanical means such as a crush or cradle or the like to physically restrain the animal. Also it is known to use drugs such as an anaesthetic to control the animal, but these drugs are often slow acting and on recovery the animal is often in a grave condition. Also unless care is taken it is possible to take the life of the animal by the careless use of drugs.
Also it is known to electrically immobilise animals, and Australian Patent No. 5561340 discloses a method and apparatus for producing a state of tetany in the animals muscles while leaving the organs in a relaxed condition by passing a pulsed electric current through the animals muscles. Reference is also made to U.S. Pat. No. 4,237,896 in this regard which is directed to a corresponding invention. The immobilisation of animals is achieved in a quick, safe manner so that operations such as dehorning, shearing, castration etc., and other forms of surgery may be carried out in the field or elsewhere in an efficient manner, with the minimum of physical effort being required to restrain the animal. The animal is immobilised by the passage of the small electric current through the nerve and muscle tissue thus causing tetany, that is the contraction of the muscles thus immobilising the animal and effecting the nervous system in such a way that the animal is not conscious of any pain when the current is applied.
There are also various patents relating to electro-anaesthesia, such as SU 1074543, SU 102277, SU 906579, SU 776613, U.S. Pat. No. 4,383,522 and FR 2457696, these being predominantly directed to human use. Also U.S. Pat. No. 4,256,116 describes the supplying of pulsing current to spaced electrodes in a patient, the current being supplied to the spaced electrodes in succession for pain relief.
SU 1435261 is directed to a post-operative analgesia method involving local treatment with a pulsing current with one electrode placed in the base of the wound and the other parallel to it and extending into the subcutaneous fat, While SU 1068127 describes the healing of post-operative wounds by the use of a sinusoidal current, the voltage being increased until the appearance of contraction of muscles in the wound area.
A pulse generator for a pain blocking bandage is disclosed in GB 2,099,705, in which there is provided a feedback circuit to supply spaced bursts of multiple pulses to the patient.
This invention embodies the same basic design and operational concepts as previous designs covered in our earlier patents such as AU 5561340 in that it consists essentially of a stable source of moderately high voltage to overcome typical electrical resistance in animal tissues, an oscillator controlling a switching transistor to deliver current pulses of a fixed duration at fixed intervals to the subject animal, and a current sensing device simultaneously controlling the switching transistor to enable the operator to control the amplitude of these current pulses.
Whilst this original design has been successfully manufactured and used throughout the world for many years, difficulty has sometimes been experience by operators in electing the most effective setting of current amplitude at switch-on for a given animal to give sufficient initial immobility without causing discomfort and distress.
Thus it would be highly desirable to be able to apply the apparatus and method to an animal without startling the animal, and to be able to further control the blockage of pain in an animal, and the present invention is directed to this end.
Experiments over many years have shown that providing a means of gradually increasing the amplitude of pulses from zero to the point of immobilisation has done nothing to improve the situation but rather tends to increase the level of discomfort felt by the animal, provoking violent movements potentially dangerous both to the operator and the animal itself.